Hydraulic jack



May 2o, 1958 M. A. RHoADs HYDRAULIC JACK 4 sheetssneet 1 Filed March 19, 1954 4 Sheets-Sheet 2 M. A.` RHoADs HYDRAULIC JACK /f j dw .JI!I[ 1 fdd, 7m fri# f a 3j/i Mw, 23% y w. j y 1MM www2@ j y i M .w g V ,f M MJ y v ./y w jow M M. A-. RHoADs 2,835,541 HYDRAULIC JACK May 20, 1958 4 Sheets-Sheet 3 Filed March 19, 1954 I f www. M@ Ma@ M 5 Ma'y 20, 1958 M. A. RHoADs 2,835,541

HYDRAULIC JACK Filed March 19. 1954 4 Sheets-Sheet 4 gli? UnitedStates Patent Oice 2,835,541 Patented May zo, 195s HYDRAULIC JACK Millard A. Rhoads, St. Joseph, Mich., assignor to Auto Specialties Manufacturing Co., St. Iloseph, Mich., a corporation of Michigan Application March 19, 1954, Serial No. 417,409

2 Claims. (Cl. 309-4) This invention relates to hydraulic jacks and particularly to hydraulic jacks capable of withstanding high side thrust loads.

Many types of loads which are to be lifted by hydrauhc jacks must be lifted from a corner or a s1de thereof rather than from a central point. The point of contact between the jack and the load to be lifted accordingly describes an arc in space as it moves upwardly when lifted by the jack. Since the jack is preferably nonshiftable with respect to the load during operation, the upper loadcarrying portion of the jack must also describe an arc in space as the load is lifted.

The movement ofthe load in an arcuate manner during lifting imposes side thrust loads on the jack, these loads being accentuated by tilting of the base to one corner thereof. This accentuated side thrust load is transmitted to the ram cylinder in prior constructions and this side thrust load tends to break the seal between the ram cylinder and the base thereby causing leakage of hydraulic uid. Alternatively the side thrust load is transmitted to the outer reservoir cylinder, this causing leakage at the junction between the reservoir cylinder and the base.

Accordingly, it is an object of the present invention vto provide an improved hydraulic jack; more specifically it is an object of the invention to provide an improved hydraulic jack which will safely carry high eccentric or side thrust loads Without leakage.

Another object of the invention is to providean improved hydraulic jack having a base which is shaped and formed to permit the jack to carry eccentric side thrust loads with less stress on the jack.

vlin connection with the foregoing object it is another object of the invention to provide vin hydraulic jacks a base which is tapered on all sides to centralize the load on the jack base when the upper end of the jack describes an arc when lifting loads.

Yet another object ofthe invention is to provide in hydraulic jacks an improved ram cylinder and method of mounting the ram cylinder.

In connection with the foregoing object it is another object of the invention to provide improved sealing means between the ram cylinder and the base and ram cylinder head.

Still another object of the invention is to provide an improved one-piece reservoir shell construction in which the reservoir and head are formed integral, this structure providing simplicity of assembly and minimizing failures due to deflection when the ram `is in raised position and is subjected to side thrust loads.

Still another object of the invention is to provide in hydraulic jacks an improved ram cylinder which is free to move at both ends with respect to the associated jack parts, this movement being carried out in a sealed manner thereby eliminating unseating of the ram cylinder and permitting lateral deflection of the ram cylinder without unseating when the jack is subjected to side thrust loads.

A further object of the invention is to provide in hydraulic jacks a novel porting structure to limit upward movement of the ram.

A still further object of the invention is to provide 1n hydraulic jacks an improved hydraulic pump structure.

A further object of the invention is to provide 1n hydraulic jacks an improved and simplified ram structure.

These and other objects and advantages of the invention will be better understood from the following description when taken in conjunction with the accompanying drawings. In the drawings wherein like reference numerals have been utilized to designate like parts throughout:

Fig. 1 is a view in vertical section of a hydraulic jack made according to and incorporating the principles of the present invention; Fig. 2 is a plan view of the Fig. 3 is a partial end view Figs. l and 2;

Fig. 4 isa partial view in vertical section of a second form of the present invention; j

Fig. 5 is a partial view in vertical section of a third form of the presentinvention, the ram being shown in the lowered position;

Fig. 5a is an enlarged partial view illustrating the ram cylinder and porting structure of Fig. 5;

Fig. 6 is a view of the jack shown in Fig. 5, the ram being shown in the upmost position;

Fig. 6a is an enlarged partial view showing the head and porting structure in the upmost position;

Fig. 7 is a partial view in vertical section of a fourth modification of the present invention;

Fig. 8 is a partial view modification of the present invention;

Fig. 8a is an enlarged partial view illustrating the seal between the ram cylinder and the base of Fig. 8;

Fig. 9 is a partial view in vertical section showing an improved hydraulic pump useful in the hydraulic jack of the present invention;

Figure 10 is a side elevational view partly in cross section of the sixth form of the present invention and showing the ram in an intermediate position;

Fig. ll is a partial enlarged cross sectional View showing the joint between the reservoir cylinder and the base of the jack illustrated in Fig. l0 of the drawings; and

Fig. l2 is an enlarged partial cross sectional View showing the junction between the ram cylinder and the base of the hydraulic jack shown in Fig. 10.

Referring now to the drawings and particularly to Figs. l, 2, and 3 there is shown a first preferred embodiment of a jack made in accordance with and incorporating the principles of the present invention. There is provided a base 20 which as can be seen in Fig. 2 is generally rectangular in shape with rounded corners. There is provided at one end on base 20 a generally circular upstanding portion Z2 on which are mounted a reservoir cylinder 24 and a ram cylinder 26. Reinforcing portions 28, 3f), 32 and 34 are provided around portion 22.

From Fig. 1 it will be seen that base portion 22 has an upstanding circular flange 36 which is externally threaded as at 38 and thereadedly receives the lower end of the reservoir cylinder 24. Reservoir cylinder 24 is substantially circular in cross section and tapers upwardly, being provided l'at its upper end with an integral reservoir head 40. Sealing between cylinder 24 and base 20 is provided by aresilient and circular O-ring 42 which is positioned within a channel 44 that is formed in the lower end of cylinder 24. Channel 44 is substantially square in cross section. O-ring 42 provides a static seal between cylinder 24 and base 20. The reservoir head 40 is hexagonally shaped as vis best seen in' jack shown in Fig. l;

of the jack base shown in in vertical section of a fifth Fig. 2 so that the cylinder 24 can be screwed down upon threads 38 and seal 42 to provide a uid tight connection between cylinder 24 and base 20.

The ram cylinder 26 is circular in cross section and has its lower end positioned in a recess formed in base 20. The upper end of cylinder 26 extends above a shoulder 46 formed on reservoir head 40 but terminates short of the upper inner wall 48 of head 40. The t between the upper end of ram cylinder -26 and head 40 is a sliding t, cylinder 26' being received by a circular aperture in head 40. A sliding tit is also made between the lower end of cylinder 26 and the base 20. The recess in base is only slightly greater in diameter than the outer diameter of cylinder 26. A fluid tight seal between cylinder 26 and base 20 is provided by a resilient and circular O-ring '50 positioned in a circular groove adjacent the lower end of cylinder 26. The above described construction and mounting of ram cylinder 26 preserves the seal between the cylinder 26 and base 20 if there is any movement .of reservoir head 40 with respect to base 20.

IMounted within ram cylinder 26 is a substantially circular ram 52 whose external diameter is less than the internal diameter of cylinder 26. Mounted on the lower end of ram 52 is a ram spacer 54 received on a smaller portion 56 of ram 52. Spacer 54 is rectangular in cross section and has an overall external diameter just slightly less than the internal diameter of cylinder 26 whereby to provide a close lit between spacer 54- and cylinder 26.

There is provided beneath ram spacer 54 a resilient pressure cup seal 58 which provides a good seal with ram cylinder 26. The seal between cup seal 5S and cylinder 26 is fluid tight for purposes which will be understood better from a later portion of the description. Cup seal 58 is held in position by a washer 6'0 which in turn is held in assembled position by a nut 6l engaged by a threaded stud 62 on the lower end of ram 52. Stud 62 and nut 61 yserve to hold washer 60 against cup seal 58 which is in turn held against ram spacer 54.

The upper end of ram 52 extends through a circular opening in reservoir head 40 and is provided with a cylinder aperture 64. The upper end of aperture 64 is enlarged to receive a threaded bushing 66 which is press tted into the upper end of ram 52. The threads on bushing 66 threadedly receive a screw extension 63 which has a narrowed portion 70 extending from the upper end thereof. Portion 70 receives a load rest 72, portion 70 being peened over as at 74 to retain load rest 72 in operative position thereon.

The upper end of ram 52 and its associated load rest 72 extend through a circular opening 76 formed in reservoir head 40. The diameter of opening 76 is slightly greater than the external diameter of ram 52 so that ram 52 will not be bound as it moves upwardly or downwardly with respect to reservoir head 40. A secondary oil seal and wiper is provided by a circular resilient O- ring 78 which surrounds the upper end of ram 52 and is received in a circular recess formed in the walls of head 40 defining opening 76.

Upward movement of ram 52 is provided by pumping oil into the lower end of ram cylinder 26. For this purpose a pump generally designated by the numeral 80 is provided. Pump 80 includes a pump cylinder 82 which is threadedly connected as at S4 to an apertured boss 86 formed on base 20 at the end thereof opposite base portion 22. Mounted within cylinder 82 is a piston 88 which is mounted for reciprocal motion therein. The lower end of piston S8 is provided with a resilient cup seal 90 which is held in place by a washer 92, a stud 94 and a nut 96. A resilient dust wiper 98 is provided around piston 86 at the point where it receives cylinder 82 and a cap 100 is provided to hold the dust wiper 98 in operative position.

Vertical reciprocation of piston 88 is accomplished by means of the handle socket 102 which is adapted to 4 receive an actuating handle (not shown) Handle socket 102 is pivotally connected to the 'upper end of 'piston 88 at point 104 and is similarly pivoted by means of a pin 106 to a link 108. Link 108 is in turn pivoted by a pin 110 to base 20. Vertical reciprocation of handle socket 102 about pivot point 106 serves to move piston 108 upwardly and downwardly whereby to cause the piston 83 and the cylinder 82 to act as a pump.

The various connections from pump 80 to the hydraulic reservoir and the ram cylinder can be best seen in Fig. 2. A first bore 112 is provided in base 20, one end of bore 112 connecting with the hydraulic uid reservoir and the other end being closed by a plug 114. A transverse bore 116 connects bore 112 with the bottom of pump cylinder S2. Positioned within an enlargement of bore 112 is a ball 118 which is pressed against an associated seat by a compression spring 120. When piston 88 is moved upwardly hydraulic tluid is taken from the reservoir through bore 112 past ball 118 which is forced to the right against the action of spring 120 and into pump cylinder 32.

Discharge from cylinder 82 occurs through an enlarged passage 122 which connects with another bore 124 that leads to the interior of ram cylinder 26. There is positioned in one end of bore 122 a ball 126 which is held in position by a spring 128 under compression. Spring 128 is held in position by a plug 130.

When the piston 88 is forced downwardly against a column of hydraulic tluid in cylinder 32, ball 126 is forced against spring 128 and compressing spring 128 thereby opening passage 122 and permitting flow of hydraulic iluid into the ram cylinder 26. Reverse ow through passage 112 is prevented by ball valve 118. On the upstroke of piston 88 passage 112 is closed by ball valve 126 which is moved to the closed position by compression spring 128. By this arrangement hydraulic iluid under pressure can be pumped into ram cylinder 26 whereby to raise the ram 52.

Rapid releasing of the hydraulic uid within cylinder 26 is achieved by a release valve 132 which when opened directly connects cylinder 26 with the hydraulic fluid low pressure reservoir. lt will be seen that opening of release valve 132 will cause a rapid lowering of ram 52 if a load is resting on load rest 72.

When ram 52 reaches the upmost position it is desirable to open the ram cylinder 26 so that the hydraulic pressure generated by pump 30 will not burst the jack structure. To this end there is provided an up-limit port 134 formed in the wall of ram cylinder 26 adjacent the upper end thereof. Port 134 is positioned so that the lower edge of cup seal 58 will be above port 134 when ram 52 is in the upmost position. This permits hydraulic fluid pumped from cylinder 82 to be 'oy-passed directly to the hydraulic fluid reservoir in an automatic manner.

There is also provided in reservoir head 40 a port 136 which provides a means of escape of hydraulic uid in greater volume from the inside of cylinder 26 into the reservoir for the hydraulic fluid. This permits ready return of any oil which escapes past cup seal 58 back to the reservoir. l

If the jack of Figs. l to 3 is used to lift a load at a corner or on the edge thereof so that the point of contact by the load rest 72 and the load describes an are, the load will not be transferred to the corners of the base but instead will be transmitted to an intermediate point 127 on the base and thus reduce the strain on the jack. This is due to the fact that base 20 has a flattened central bottom portion 129 which extends to line 127. The base then tapers upwardly and outwardly along surface 131 (see Fig. 1) and surfaces 133 and 135 (see Fig. 3) to the edges of base 20. The reservoir cylinder 24 is formed of steel so that its elastic properties can be used to take up the strain of sidewise thrust upon the jack structure.

75 Leakage under such strained conditions is prevented by vls the ring 42 and the integral construction between the- Referring now to Fig. 4 a second form of the jack of the present invention will be described. There is provided in this form of the invention a base 140 generally similar to base 20 and having an upstanding externally threaded flange 142. A reservoir cylinder 144 threadedly engages llange 142 as at 146 and is sealed to base 140 by an 0ring 148.

" There is also a ram cylinder 150 which is threadedly attached to base 140 as at 152 instead of having a slide contact therewith as was the case in the jack of Figs. l to 3. A circular 0ring 154 provides a fluid tight seal between ram cylinder and base 140.

There is provided within ram cylinder 150 a ram 156 provided at its lower end with a ram spacer 158, a pressure cup seal 160, a washer 162 and a stud 164 which hold the washer 162, the seal 160 and the ram spacer 158 in assembled position on ram 156. These parts operate in the same manner and perform the same functions as. the corresponding parts in Fig. l.

Referring now to Figs. 5', 5a, 6 and 6a there is shown a third embodiment of the present invention. This form of the invention includes a base 170 which has an upstanding flange 172 formed thereon. The bottom of base 170 has a llat section 174 and an upturned section 176 which is disposed at an angle with respect to the flat section 174. A reinforcing rib 178 is provided to give added strength. The base is also provided with upturned bottom sections on the elongated parallel sides thereof as was the base of Fig. l.

Threadedly attached to base 170 is a circular reservoir cylinder 180 which is threaded to base 170 as at 182. The upper portion of cylinder 180 is internally threaded to receive and cooperate with a reservoir head 184. A static seal is provided between cylinder 180 and base 170 by an 0ring 186 and between cylinder 180 and head 184 by another 0ring 188.

Also mounted on base 170 and positioned concentric with respect to and within cylinder 180 is a ram cylinder 190. The lower end of cylinder 190 tits within a circular this form of the invention for the recess in base 170 and has a sliding' lit with the walls of y the recess. The upper end of cylinder 190 is similarly received in a recess formed in head 184 and forms a sliding fit therewith. A static seal is provided between v the lower end of cylinder 190 and the base 170 by a circular 0ring 192. Another static seal is provided between the upper end of cylinder 190 and head 184 by an 0ring 194 disposed within a groove 196 formed in cylinder 190.

Positioned within cylinder 190 is a ram 198 which has on its lower end a smaller portion 200. The diameter of ram 198 is considerably less than the internal diameter of cylinder 190. The smaller portion 200 of ram 198 receives a ram spacer 202 which is held thereon by a retainer ring 204 disposed within a groove formed on portion 200.

In this form of the invention the ram spacer' 202 has a sliding tit with the internal walls of cylinder 190 and serves as a guide for the lower end of ram 198. This type of ram is sometimes referred to as the displacement type, hydraulic pressure being` present on all surfaces but the net resultant force being upwardly against the lower end of ram 198. Up-limit porting is achieved by the fact that there is free llow or at least considerable escape of hydraulic fluid past ram spacer 202 and up against the main pressure seal positioned on the head 184. To accommodate the llow of such lluid past spacer 202 it is recessed on its upper face as shown at 206, this recess communicating with a vertical portion 208 which in turn communicated with a horizontal portion hole 209 in the ram 198. If further free flow of fluid past spacer 202 is desired, vertical slots may be made on the outer periphery of spacer 202. When the ram is in its uppermost position as shown in Fig. 6, up-limit porting is achieved by the escape of fluid through passage 206 and passages 208 and 209 to passage 210 formed in reservoir head 184.

A In order to retain high pressure fluid within ram cylinder 190 during upward travel of ram 198, a main ram pressure seal in the form of an 0ring 212 is provided, 0ring 212 being backed up by a washer 214 disposed in a slot formed in head 184. 0ring 212 and associated parts serve to prevent escape of hydraulic fluid during lifting of ram 198.

At the upmost limit of movement of ram 198 the upper edge of ram spacer 202 contacts the flange 216 formed on head 184. With the parts in this position the port 209 coincides with the opening to passage 210. This permits escape of high pressure fluid around spacer 202 and back to the hydraulic fluid reservoir. Another 0ring 218 serves as a secondary ram seal and wiper to prevent escape of fluid from the jack.

The upper end of ram 198 is provided with the usual load rest 220 for engagement with the load to be lifted. It is to be understood that the jack of this form of the invention is provided with a hydraulic pump and suitable valve connections to cause operation of ram 198. A detailed disclosure of these parts has been omitted in purposes of simplification.

The jack of Figs. 5 and 6 will be seen to incorporate the floating ram cylinder 190 which can move relative to the base and the reservoir head 184 without breaking the seal with these members and without taking undue stress. This feature combined with the bevelled base 170 makes this 'jack particularly suitable for lifting loads in which high side thrust are encountered.

Referring now to Fig. 7 there is shown a fourth form of the present invention. This form of the invention utilizes a base 222 which is identical inconstruction with base 170 and has mounted thereon and threadedly attached thereto a reservoir cylinder 224. Threaded to the upper end of reservoir cylinder 224 as at 226 is a reservoir head 228 having an opening 230 therein. An 0ring 232 seals the joint between cylinder 224 and base 222 and a similar 0ring 234 seals the joint between cylinder 224 and reservoir head 228.

Positioned within cylinder 224 is a ram cylinder 236 which is circular in cross section and which is received in a circular recess in base 222, cylinder 236 having a sliding and close lit with the recess in base 222. An 0ring 238 is provided in an annular groove near the lower end of ram cylinder 236 to seal the joint between base 222 and cylinder 236. The upper end of cylinder 236 is slidably received in a recess formed in head 228.

There is provided within cylinder 236 a ram 240 whose upper end extends through aperture 230 in head 228, and the ram 240 carrying a rotatably elevating extension screwload rest assembly 242. 0ring 244 seals the space between ram 240 and the wall of head 228. The lower end of ram 240 carries a Vram spacer 246, a cup seal 248,

a washer 250 and a stud 252 which holds the washer 2550,v

seal 24S and the ram spacer 246 in assembled relationship on ram 240.

A large escape avenue for hydraulic fluid trapped above cup seal 248 is provided through a port 254 formed in `head 228. Up-limit porting is provided by a port 256 7 tion. with base 20 of'` Fig;v 1 and including an opstanding threaded ange 262. A reservoir cylinder 264, is threadedly attached toflange 262 as at 266. /l

Mounted within cylinder 264 and on base 260 is a ram cylinderv 268 which is threadedly received by base 260 as atv 270 and resiliently sealing hydraulic pressure by use of O-ring 271.. Within cylinder 268 is positioned a ram 272 having at its lower end a ram spacer 274, a cup seal 276, a. washer 278 and a stud 280 which are assembled in the same manner and perform the same function as the corresponding parts in Fig. l. An O-ring 282 seals the joint between cylinder 264 and base 260.

The upper portion of the jack of Fig. 8 has not been illustrated in full but may be identical with the upper portion of thejaclt shown in Fig. 7. The essential difference lies in the fact that the ram cylinder 268 is xedly attached to base 260 by threads 270.

An improved and simplified form of hydraulic fluid pump is illustrated in Fig. 9 and includes a base 284 within which is formed a cylinder bore 286. Within bore 286 is positioned a cylindrical piston 233 which forms a close fit with the walls of bore 236. Adjacent the upper end of bore 286 and in the wall thereof there is provided a seal about piston 288 in the form of an O-ring 290. O-ring 290 is backed up by a flat washer 292 to improve the action of O-ring 290.

The upper end of piston 288 has pivotally attached thereto by means of a pin'294 a handle socket 296 so that reciprocating motion can be imparted to piston 28S. The lower end of bore 286 empties into a transverse bore 298 which communicates with the hydraulic fluid reservoir and the ram cylinder in the usual manner.

There is shown in Figs. 10, 1l and 12 yet another form of the present invention. The jack of this form of the invention includes a base 300 having a relatively at bottom portion 302 which is bounded on either side by upturned bottom portions 304 and 306. Mounted on the upper side of base 300 is a reservoir cylinder 308 which is received in a recess in base 300 defined by an upstanding ange 310. The tit between the external base surface of cylinder 30S and the internal surface of flange 310 is tight but permits sliding movement between these parts. The joint between cylinder 308 and base 300 is sealed by an O-ring 312 positioned in a recess 314 formed on the upper surface of base 300. Referring to Fig. 11 it will be seen that recess 314 is substantially rectangular in cross section and that the O-ring 312 extends upwardly above the adjacent surface 316 of base 300. The bottom surface of cylinder 308 is tapered downwardly toward the center as at 315, the inner corner 317 digging into the O-ring 312 to provide a fluid tight seal.

Positioned within and concentric with cylinder 303 is a ram cylinder 318 which is circular in cross section and it is threadcdly received as at 320 in a recess formed in base 300. The lower end of cylinder 318 is cut away as at 322 to form a groove, the cutting away of the material along the line 322 resulting in a relatively narrow edge 324 on the lower end of cylinder 318. Positioned within the groove formed by cut-out 322 is another O- ring 326 which seals the joint between cylinder 318 and base 300. k

The upper end of cylinder 318 has fixedly attached thereto a reservoir cap 32S which extends outwardly therefrom and covers the space between cylinders 303 and 31S. Cap 328 presses against the upper end of cylinder 308 whereby to hold a cylinder 308 down against Oring 312 when the parts are in assembled position.

Positioned within the cylinder 318 is a ram 330 which extends upwardly through an opening in cap 328. The

8 lower end of ram 330 is provided with a ram spacer 332, a cup seal 334,21V washer 336 and a nut 338 which holds the washer 336, cup seal 334 andl the retainer on the ram spacer 332 on the lower end of ram 330.

Means for pumping hydraulic fluid under pressure into cylinder 318 below ram 330 is provided in the form of a pump cylinder 340 provided with a piston 342. The upper end of piston 342 is pivotally connected by means of a pin 344 to a handle socket 346. A release valve 3,48 as well as suitable internal connections are provided to conduct fluid from pump cylinder 340 to the ram cylinder 318.

The form of invention shown in Figs. 10 to 12 provides for relative movement between the reservoir cylinder 308 and the base 300 while maintaining the fluid under pressure sealed therein. The bottom of ram cylinder 318 is also sealed to base 300 in a fluid tight manner. This construction increases the capacity of the jack in that greater loads can be raised with a given size of jack. This increased capacity is achieved while the jack provides a construction having-a longer leak-free useful life.

Although for purposes of illustration circular O-rings have been shown throughout the drawings, it is to be understood that sealing rings having other cross sections but annular in shape may be used in place of the circular cross section O-rings illustrated.

1t will be seen that there'has been provided several forms of hydraulic jacks which fulfill the objects and advantages set forth above. Although certain preferred embodiments of the invention have been shown for purposes of illustration it is to be understood that various changes and modifications can be made therein without departing from the spirit and scope of the invention. Accordingly the invention is to be limited as set forth in the following claims.

I claim:

1. For use in a hydraulic jack having a base plate and uid confining cylinder, the provision of a recess in said base plate providing a cylindrical surface and a bottom surface against which the bottom of the cylinder abuts, means for securing said cylinder to said base plate an annular groove in said bottom surface spaced radially from said cylindrical surface, a resilient sealing ring positioned in said groove and projecting above said bottom surface, the inner annular corner of said cylinder overlying said groove within the edges thereof to dig into and become embedded in the portion of the sealing ring projecting above the bottom surface to an extent limited by the abutting engagement between the bottom of the cylinder and said bottom surface whereby to seal the substantially radial and vertical surfaces adjacent the said annular corner of the cylinder while protecting the sealing ring against excessive compression by the cylinder.

2. The structure claimed in claim 1, wherein the bottom edge of the cylinder is tapered downwardly toward the center thereof to increasingly dig into the sealing ring.

References Cited in the lile of this patent UNITED STATES PATENTS 1,540,906 Schweinert June 9, 1925 1,711,549 Stillman May 7, 1929 1,759,517 Miller et al May 20, 1930 1,936,669 Heeter Nov. 28, 1933 2,070,935 'lraut Feb. 16, 1937 2,527,428 Kernerer Oct. 24, 1950 2,563,912 Belinkin Aug. 14, 1951 2,627,722 Johnston Feb. 10, 1953 2,672,014 Yarger Mar. 16, 1954 2,723,528 Stark et al Nov. 15, 1955 

